A brief review of the field of underpotential deposition (UPD) processes in the theory/modeling perspective is given, and new insights into the UPD of copper and silver on Rh(1 1 1) and Rh(1 0 0) in perchloric and sulfuric acid media are reported. Voltammetric results show a clear dependence of the UPD shift on Rh substrate geometry and on the type of the electrolyte used. For copper, we identified one peak on Rh(1 0 0) and two peaks on Rh(1 1 1), separated by 210 and 350 mV in perchloric and sulfuric electrolytes, respectively. Preliminary XPS experiments were performed to investigate some specific aspects of copper deposition processes. Overall, we report a strong effect of the anion adsorption on positions of Cu UPD peaks, with the effect being more noticeable on Rh(1 1 1) than on Rh(1 0 0). In the experiments with silver on Rh(1 1 1), multiple peaks were obtained, whereas no Ag UPD peak was found either on Rh(1 0 0) or on polycrystalline Rh. In addition, we found that the Ag UPD process on Rh(1 1 1) is dependent on silver concentration. As indicated in the paper Tables, except for Cu UPD on Rh(1 0 0), there is a major deviation from the linear relationship between the UPD shift and the difference between the work function of the substrate and that for the underpotentially deposited adatoms. (C) 2009 Elsevier B.V. All rights reserved.